This patent generally relates to displays and particularly to large display systems comprising groups of light emitting elements. The invention discloses improvements in the calibration of the light emitting elements.
Large display systems for entertainment, architectural, and advertising purposes have commonly been constructed of numbers of light emitting elements, such as LEDs or incandescent lamps mounted onto flat tiles. The light emitting elements can be selectively turned on and off to create patterns, graphics and video displays for both informational and aesthetic purposes. It is well known to construct these displays as tiles or large panels which are assembled in position, such as on a stage, for a specific entertainment show or event, or as an architectural or advertising display, such on the tops and sides of buildings.
Many of these systems require large numbers of light emitting elements or pixels acting independently and thus require robust high speed data distribution systems, often driven by computer derived data or video signals.
A requirement of such displays is that the light emitting elements for all pixels on the display be matched within a reasonable tolerance for color and luminance intensity. For example, in a large display comprising many thousands of pixels, each of which may include at least a red, green, and blue LED, an object should appear the same color and brightness wherever it is on the display. Light emitting elements, such as LEDs and their associated drive circuitry, are not manufactured to a close enough tolerance to allow their use uncalibrated in such displays. Although the manufacturers of LEDs sort their production into bins by nominal intensity and color, the tolerance of these bins are not good enough for this demanding application. It is therefore advantageous to adjust or calibrate the output of every LED individually so that an even and cohesive display is produced. Conventional display calibration techniques utilizing calorimeters and luminance meters can be prohibitively expensive and time consuming when applied to a large display having very large numbers of pixels. Such procedures typically use stored CIE chromaticity coordinates and luminance information to calculate the transformation matrices for color calibration. However, such techniques do not allow the display to be operated at different color standards without recalibration, nor do they allow for the differences in photopic (day-time) and scotopic (night-time) vision.
The invention seeks to solve these problems and discloses improvements in the measurement, characterization, and calibration systems for a display comprising groups of light emitting elements so as to provide improved accuracy and flexibility of such calibration across any color space.